This paper describes the ignition transients of a LOX/ethanol gas generator that is used for a gas generator cycle air turbo ramjet engine. It is essential to know the temperature history of the LOX injector manifold in order to determine the appropriate ignition sequence. Following a chill-down process, an inert gas purge is performed prior to ignition. Once the main valve is opened, liquid oxygen is discharged after a short period of discharging gaseous oxygen. The period of the gas discharge is a critical parameter for the success of the ignition that is affected by the injector temperature at the time that the valve opens. As a result of the experiments, the gas discharge period was found to be in the range of 0.5–1.0 second, whereas the injector temperature when the valve was opened ranged from 120–170 K under various experimental conditions.